Heart of the Swarm's campaign has been under wraps for more than a year. James travels to Blizzard's headquarters in Irvine, and reports back on what to expect come the 12th of March.

Few would argue that Blizzard excels at creating expansion packs. Playing Diablo II without the Lord of Destruction add-on seems like a ridiculous proposition. We can recall fondly the high fantasy drama of Warcraft III: The Frozen Throne, and many consider World of Warcraft: The Burning Crusade to be the MMO’s high watermark.

But perhaps none of these have had quite the same impact as StarCraft’s Brood War expansion. The add-on is frequently credited with facilitating the early rise of eSports, particularly in Korea, and its sweeping campaign was a gripping elaboration of the sci-fi universe and its lore. It remains one of the most important real-time strategy releases to date.

So it must be with some trepidation that gamers and Blizzard alike look toward to the release of StarCraft II’s first expansion on the 12th of March. In the wake of such illustrious siblings, expectations for Heart of the Swarm are very high indeed.

Heart of the Swarm continues StarCraft’s epic of sacrifice and betrayal, impending doom and flickering hope. Sarah Kerrigan was a covert Ghost operative left to die by the ruthless leader of the Terrans, Arcturus Mengsk – only she didn’t. Instead, she was captured by the xenomorphic Zerg and assimilated into the Swarm. Reborn as the Queen of Blades, Kerrigan led the Zerg on a rampage across the Korpulu sector, but her old flame, the idealistic rebel Jim Raynor, never stopped believing that her humanity remained suppressed deep within.

In StarCraft II: Wings of Liberty the tenacious Raynor and his ragged band of Terran allies defeat the Zerg, and Kerrigan appears to have been returned to her human form. But even now, the Queen of Blades still lingers within Kerrigan, and her lust for vengeance has not abated:

THE DARK MIDDLE CHAPTER

In Heart of the Swarm, players control Kerrigan as she seeks to rebuild her power, and re-establish her dominion over the Zerg. The game has a much darker tone than Wings of Liberty. It’s a campaign that game director Dustin Browder hopes will give players a better sense of what it means to be a monster.

“It gives you a sense that Kerrigan has problems that Raynor just doesn’t understand. Kerrigan has much more serious concerns, she is in a much bigger universe than he is with much more serious issues, and she can’t always get away clean. Raynor can always find a way to make it work, to still be the good guy.

“Kerrigan sometimes has to make the hard call. She’s surrounded by these creatures that don’t understand her, that are not sympathetic to her, and she doesn’t always understand them either. That’s what we’re going for: this is the dark middle chapter of the trilogy.”

Last week, members of the press were invited to play a handful of missions part way into the campaign. Kerrigan is reclaiming feral Zerg swarms on the icy planet of Kol’dir, and as she does so, she must also contend with small settlements of Protoss who are always a mere warpgate away from alerting the mighty Golden Armada to her presence.

In the campaign, Kerrigan will be a powerful hero unit that players will level up. As they do so, they’ll be able to choose from pairs of abilities that will increase her effectiveness on the battlefield. Even this early in the game, Kerrigan is remarkably powerful, and it’s something that radically changes the dynamics of campaign play when compared next to Wings of Liberty.

“She feels mighty – no question – and that’s what we want,” says Browder. “She can be a third or even half of your firepower, or if you want to kit her more passively, where she’s buffing the swarm, you can kit her that way.”

It’s also a significant departure from an earlier build of the campaign that Gameplanet saw over a year and a half earlier. Then, Kerrigan had load-outs to choose from, or, as Browder calls it, “different flavours of Kerrigan.”

“What would happen was that players would find their favourite version of Kerrigan and then never switch. What’s the point in that? It didn’t provide anyone with the challenge of new choices. Now, as you’re going up you’re adding more and more powers, adding to things you can do, and it means you’re playing with more toys on the battlefield.”

A SPLICE OF LIFE

Just as Kerrigan can mutate and evolve her powers, so too can her Swarm. As players advance through the early missions, they’ll unlock new types of Zerg units, and these can be upgraded in two ways. Mutations present players with one of three options that will tweak the power of each unit type. For example, player might choose to mutate a unit for longer range, larger splash damage or more resilience.

Evolutions are more complex, and permanent. Abathur, the Zerg creature that oversees the evolution of Kerrigan’s Swarm, will task her with small DNA-gathering missions that showcase the evolution options for each unit type. One mission might see Kerrigan with assimilating Zerg banelings that have evolved and learned how to jump up and down cliffs. Another might see her splicing baneling DNA with creatures that, upon death, split to create two smaller versions.

Unlike Wings of Liberty, however, structures will not be customisable. “We did discuss it some, and we tried a number of things: we had a Spore-Spine Crawler combo for a while, we had Spine Crawler with two tentacles on it – that was kind of fun. But we’re really trying to get away from the Zerg defending a lot,” says Browder. “We want the Zerg to be attacking and we’re trying to organise our mechanics around that.”

“We want you to be very aggressive, always attacking and sacrificing units – all for the greater good of the Swarm. That’s been a challenge for us in the campaign, because you know most players start to feel – even for the Zerg – some empathy, and they don’t want to lose troops. So that’s what we’re trying to push players towards.”

THEY MOSTLY COME OUT AT NIGHT

True to Browder’s vision, the majority of the missions shown to press coaxed aggressive play. Objectives are hidden deep behind enemy bases, and other timed events also demand a more offensive approach. At normal difficulty, what few raids the computer does carry out on Kerrigan’s bases are quickly repelled or outright negated with only the most cursory of defences.

However, the final, and most memorable mission shown was altogether different. A Protoss spacecraft has slipped though Kerrigan’s web, but the resurgent Queen of Blades has managed to smuggle a single, embryonic spawnling aboard.

The level begins almost as homage to Ridley Scott’s Alien: the defenceless spawnling must avoid Protoss detection by hiding in shadows and crawl spaces, and by infesting research samples stowed aboard. Finally, the spawnling is strong enough to find a secluded area and mutate into a broodmother capable of spawning Zerg units of her own. Subsequently, she and her brood gut the husk of the ship.

It’s a dynamically different passage of gameplay, but one that fits perfectly with the Zerg tone.